<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>throttle</title>
  </head>
  <body>
    <script>
      function throttle(fn, delay = 200) {
        let timer = null;

        return function () {
          if (timer) {
            return;
          }

          timer = setTimeout(() => {
            fn.apply(this, arguments);
            timer = null;
          }, delay);
        };
      }
    </script>
  </body>
</html>
